The proposed 4-year project will be the first to investigate the effects of measured school environments on cognitive development and academic achievement using a genetically sensitive design. The proposed research will test the hypothesis that genes play a part in mediating the effects of the school environment on educationally relevant behaviors, that is, that children actively select, modify and create environments that are correlated with their genetic propensities. It is also hypothesized that educational influences on cognitive development and academic achievement involve non-shared as well as shared environment. That is, even twins in the same classroom experience different educational environments and these nons-hared environments affect educational outcomes. The project will capitalize on a large twin study of behavioral development in childhood in which 7500 twin pairs born in 1994-96 have been assessed at 2, 3, 4 and 7 years on measures of cognition, language and behavior problems. We plan to assess each child's school and classroom environments at 10 years of age as perceived by the children themselves, as well as their parents and teachers. We will also assess cognitive development and academic achievement in order to test the hypothesis that school environments and their relationship to educational outcomes are in part mediated by genetics. The significance of finding genetic influence on educational experiences and their association with educational outcomes comes from bridging the gulf between the fields of education and genetics. Finding genetic influence will not denigrate the role of education but will suggest new ways of thinking about effective education, such as recognizing that children create their own experience within the educational process in part on the basis of their genetic propensities.